The National Academy of Sciences and the Environmental Protection Agency have reported that up to 15% of the general population may have heightened sensitivities to low levels of certain gases which are exuded, over time, from many commonly used construction materials and which eventually become constituents of the internal atmosphere of virtually every kind of building constructed according to past or present construction methods. Persons having such increased sensitivities generally react to such gases much in the same way as those who are allergic to pollens, molds, dust, insects, and animal danders. That is to say that such gases act as immunogens; i.e., capable of inducing and perpetuating undesired immunological responses in susceptible individuals. Very often those individuals who are allergic to pollens, molds, etc. are also sensitive to such gases. To a large extent such findings were the motivating force behind legislation (e.g., U.S. Senate Bill 657) designed to address this problem.
Unfortunately, most of that segment of the population predisposed toward such susceptibilities are often particularly sensitive to those gases given off by many petrochemicals commonly used in the manufacture and/or coating of a wide variety of construction materials. For example, many wood and lumber products used in framing buildings of all kinds are usually treated with various petrochemicals during the course of their manufacture. Moreover, some woods, and especially certain soft woods (e.g., cedar, redwood and certain conifers), also give off gases of certain of their natural constituent chemicals (e.g., terpenes) and such gases are generally regarded as being particularly harmful to those having such chemical susceptibilities. Other naturally occurring gases which are often associated with buildings (e.g., radon and methane) emanate from the ground and accumulate in the building's atmosphere, especially in basement areas. Gases of these kinds are generally regarded as being toxic to all members of the general population. Therefore, and particularly in regard to the matter of housing people having known chemical susceptibilities, not only should new buildings be designed with a view toward dealing with any specific known chemical sensitivities and/or allergic conditions of the intended occupants, they also should be designed with a further view toward minimizing any less severe, but still undesirable, immune response reactions and/or any general toxic reactions in the more general population.
At this point perhaps it should be noted that although certain terms such as "immunogen", "allergen", and "antigen", are frequently used interchangeably when discussing undesirable immune responses, these terms are not necessarily synonymous. Immunogenicity, for example, may be defined as the capacity of a substance to initiate a humoral or cell-mediated immune response, whereas antigenicity may be defined as the capacity of a substance to bind specifically with those antibody molecules whose formation it has elicited. The word ligand also has been employed to describe the latter property of specific binding to antibodies. Employed precisely, the term immunogen also specifies that a substance acts at the afferent limb of the immune response. Those skilled in the medical arts will also appreciate that many antigens will possess both immunogenic and antigenic capacities, even though, in some instances, these two attributes may not be apparent due to a state of immunologic unresponsiveness or due to a genetic inability of certain human beings to respond to certain antigens.
Similarly, those skilled in the medical arts will also recognize that allergens are a special group of antigens which are innocuous to the majority of the population, but which may nonetheless cause disease when predisposed individuals are exposed to them by inhalation, ingestion, injection, or by contact with the skin surface. Allergens may be very large molecules such as proteins, polysaccharides, polypeptides and polynucleotides (a large majority of the common, naturally occurring allergen substances such as ragweed, grass pollens and the like usually have rather complex molecules having molecular weights of up to 40,000 and they frequently contain both protein and carbohydrate components); or they may be relatively simple, low molecular weight compounds (e.g., terpenes, sulfadiazine, etc.) which usually require an association with protein carrier molecules in order to elicit an immune response, at least during the immunogenic phase.
It should also be noted in passing that many atopic diseases of this kind tend to manifest themselves in individuals with a hereditary predisposition to produce IgE reaginic antibodies on exposure to such environmental allergens. There is also a great deal of evidence to suggest that atopic individuals may have an increased sensitivity to certain chemical mediators of allergic reactions such as histamine, acetylcholine or prostaglandins. Nonetheless, all of the above differences notwithstanding (or unless otherwise stated), the terms immunogen, allergen and antigen will be used more or less interchangeably throughout this patent application when describing substances having immunogenic capacities, antigenic capacities and/or allergenic capacities. It also should be noted at this point that applicant may also use the terms "hypoimmunogenic", "nonimmunogenic" and like terms of diminution or negation of the subject of immunogenicity in order to describe certain materials employed in, as well as certain environmental conditions achieved by, the practice of the herein disclosed methods of construction.
In all cases however, in considering the action of immunogens, antigens and/or allergens in either atopic or in normal individuals, the portal of entry of such immunogenic substances is of great importance; and it cannot be gainsaid that those individuals who are genetically or otherwise predisposed to the development of such atopic reactions are usually sensitized by exposure to an immunogen by way of the bronchial mucosae. There still exist some questions as to whether or not a specific form of interaction between the mucosal lining and the immunogen (or a defect in mucosal integrity) is required for a material to enter the body in an immunogenic form; but regardless of the answers to these questions, almost all would agree that provision of an environment with reduced levels of gaseous immunogenic substances can only serve to help hypersensitive individuals as well as the more general population.